docs: def plot_lc(calc_id, aid=None):
      """
      Plot loss curves given a calculation id and an asset ordinal.
      """
      # read the hazard data
      dstore = util.read(calc_id)
      dset = dstore['agg_curves-rlzs']
      if aid is None:  # plot the global curves
          plt = make_figure(dset.attrs['return_periods'], dset.value)
      else:
          sys.exit('Not implemented yet')
      plt.show()